Carbon Nanotube Microwell Array for Sensitive Electrochemiluminescent Detection of Cancer Biomarker Proteins

Abstract

This paper describes fabrication of a novel electrochemiluminescent (ECL) immunosensor array featuring capture-antibody-decorated single-wall carbon nanotube forests (SWCNT) residing in the bottoms of 10 µL wells with hydrophobic polymer walls. Silica nanoparticles containing [Ru(bpy)3]2+ and secondary antibodies (RuBPY-silica-Ab2) are employed in this system for highly sensitive two-analyte detection. Antibodies to PSA and IL-6 were attached to the same RuBPY-silica-Ab2 particle. The array was fabricated by forming the wells on a conductive pyrolytic graphite chip (1 × 1 in.) with a single connection to a potentiostat to achieve ECL. The sandwich immunoassay protocol employs antibodies attached to SWCNTs in the wells to capture analyte proteins. Then RuBPY-silica-Ab2 is added to bind to the captured proteins. ECL is initiated in the microwells by electrochemical oxidation of tripropyl amine (TprA), which catalytically reduces [Ru(bpy)3]2+ in the 100 nm particles, and is measured with a coupled charged device (CCD) camera. Separation of the analytical spots by the hydrophobic wall barriers enabled simultaneous immunoassays for two proteins in a single sample without cross-contamination. Detection limit (DL) for prostate specific antigen (PSA) was 1 pg mL−1 and for interleukin-6 (IL-6) was 0.25 pg mL−1 (IL-6) in serum. Array determinations of PSA and IL-6 in patient serum were well-correlated with single-protein ELISAs. These microwell SWCNT immunoarrays provide a simple, sensitive approach to detection of two or more proteins.

Label-free electrochemical detection of human methyltransferase from tumors

“…Electrochemistry has been used to detect nucleic acids with high sensitivity and without the need for PCR amplification in bacterial lysate and serum (18)(19)(20)(21)(22), but protein detection remains a challenge (23)(24)(25)(26). In fact, although protein detection from simple serum has been accomplished (27,28), to date no reported electrochemical systems have effectively detected active protein, of any kind, from crude cell lysate.…”

Development of Solid-State Electrochemiluminescence (ECL) Sensor Based on Ru(bpy)32+-Encapsulated Silica Nanoparticles for the Detection of Biogenic Polyamines

“…-encapsulated silica nanoparticles (RuNPs) was done according to the previously published micro emulsion method [25][26][27]. The water-in-oil micro emulsion was prepared by mixing 1.77 mL of TX-100, 7.5 mL of cyclohexane and 1.8 mL of 1-hexane.…”

Properties and Customization of Sensor Materials for Biomedical Applications

“…Rusling et al (253) employed SW-CNTs forests for the electrochemiluminescent detection of interleukin-6 (IL-6) and PSA, two cancer biomarker proteins. A charge-coupled device (CCD) camera was then used for the detection of the light generated by the silica NPs labeled with a ruthenium dye and the specific antibody, achieving detection limits of 1 pg ml À1 for PSA and 0.25 pg ml À1 for IL-6 (254,255).…”